I have a 12V 60Ah EFB battery in a 3-year old start/stop car.
The battery doesn't seem to hold a charge. Is there any way to estimate / understand how much longer it can last, or if it's best to replace it now?
I never left it unused for more than 2 weeks, except now, under quarantine, when I charged it with a charger after about 3 weeks without using it, but I did use it a lot for relatively short trips which may have never fully charged the battery (I didn't measure).
24 hours after a full charge, a multimeter measured 12.35V.
7 days after a full charge, it measured 12.1V. Both times without using the car.
I recharged it again but noticed the same: 12.35V after 1 day and 12.1V after 7 days.
There is no alarm or GPS tracker to justify a huge parasitic drain.
The charger is an Optimate 5 start/stop which can specifically handle EFB batteries.
If I used the car every day for long journeys I wouldn't be worried, but with the world under quarantine I won't, and I am afraid the battery could die just when I need the car.
Any suggestions? Thanks!